Question : issue with email from outlook but it works with telnet and smtp

i am sending an email to an outside domain using outlook but i get undeliverable
Your message did not reach some or all of the intended recipients.

      Subject:      test
      Sent:      11/2/2009 12:09 PM

The following recipient(s) could not be reached:

      [email protected]' on 11/2/2009 12:09 PM
            The e-mail address could not be found.  Perhaps the recipient moved to a different e-mail organization, or there was a mistake in the address.  Check the address and try again.
           

but when i telnet to the other exchange server and send an email via telnet it goes through and the users replies back to me.
What is the issue ?
I crealed the cache on my outlook , retyped manually the email address but still undeliverable.

Answer : issue with email from outlook but it works with telnet and smtp

Could be a DNS issue?

If you are on the Exchange server, go to command prompt and type:

nslookup -q=mx domain.com

Does this show the correct server? The one you used in your telnet?

Does Exchange have an external DNS servers configured? http://technet.microsoft.com/en-us/library/aa998213.aspx. If so are they correct?

Shaun